BS AU 50-3.8:1985 download.Tyres and wheels Part 3: Valves Section 8: Code of practice for the selection and care of tyre inflation valves for commercial vehicles.
8.1 Scope
Th section of BS AU 50-3 gives recommendations for vehicle manufacturers on the initial steps to be taken in selecting valves for commercial vehicle wheels and recommendations for the care of valves for the user.
8.2 Valve selection by vehicle manufacturer
When selectrng a valve for a wheel and lyre assembly it is important to ensure that the correct choice is made.
Basic factors which influence this choice are:
a) type of Lyre (tube type or tubeless); hI inflation pressure of the lyre; c) type of wheel.
The basic choice is between tube type and tubeless tyres. This would generally be decided by the vehicle design and performance requirements and the valve type is therefore predetermined.
8.3 Types of valves
8.3.1 General
Valves arc available in the following two basic types;
a) tubeless type valves, which can be either of the rubber snap-rn or metal clamp-in types (see 8.3.2):
b) tube type valves, which can be either one piece or two piece valves (see 8.3.3). g.3.2 Tubeless valves
8.3.2.1 Rubber snap in ualtes. Rubber snap-in valves art’ available in several different lengths and sizes and care should be exercised in selecting the correct size to suit the rim hole, and the moat suitable length for ease o(aocess so as not to be damaged in service.
The’ valve stem is threaded internally and externally for fitment of the valve core and valve sealing cap respectively.
It is essential that special care should be taken when fitting rubber snap-in valves, First the rim hole should be inspected to ensure it is in good condition and free from burrs and sharp edges which can damage the rubber body of the valve. Then the rubber body of the valve should be lubricated with an approved lubricant for case of fitting and inserted into the rim hole using a special valve insertion tool. To ensure that the valve is correctly located, it is essential that the moulded fitting line on the rubber valve body passes completely through the rim valve hole.
NOTK This tvpv 01 alw is osutahi. tiw lyre inflatinc pressures up La a ma.mum at 47 kPa (4.7 bar or flu psi).
8.3.2.2 Clomp-in t’alves, Metal clamp-in valves are available in a variety of sizes. It should always be ensured that the correct valve is fitted for the rim bole size and application. Clamp-in valves for tubeless truck tyres are clamped into the rim and an airtight seal is achieved by means of a hexagonal nut and rubber grommet. During fitting it should be ensured that the valve is correctly located relative to the wheel components to ensure ease of access for pressure checking and adjustment.
8.3.3 Tube valves
8.3.3.1 One piece talves. These are rubber based or rubber covered straight stem valves which are vukanized to the inner tube and bent when required to given angles and dimensions.
8.3.3.2 Th’o piece values. These conait of’ a rubber “spud” and a pre.bent stem (dimensions according to requirement) which is attached to the “spud” when required. The two piece valve is sometimes referred to as “universar.
It is essential that care is exercised to ensure correct location of the valve in the flap (where fitted) and in the rim aperture to prevent unnecessary strain on the valve in use.
If the valve is of the universal screwon type it is essential that it should be fitted with the correct rubber washer in good condiuon and sufficiently tightened to form an airtight seal by continuing to tighten down the stem a further two turns after the stem’s metal washer ha. touched the rubber washer. The valve should be aligned by additional tightening.
8.4 Valve fitting checks
Whenever a tubeless Lyre or a tyre and tube assembly is inflated or the inflation pressure is checked and/or adjusted it is essential that a final check should be made that the valve has correctly sealed. Leaking valve cores should be replaced. It should not be attempted to cure a leaking valve by extra Lightening as this may damage the core seal.
It should be ensured that the valve hole in the rim is in good condition and is free from burrs which could damage the valve and cause deflation of the tyre.
A valve cap of the type which acts as an additional air seal and which protects the core from dirt, dust and
water should always be fitted.
8.5 Valve accessibility
Where access to the valve for inflation or pressure checking purposes is difficult, a valve extension may be used.
If extensions are required to assist accessibility for inflation, deflation and pressure checking, it is important that they should be securely attached to the valve, preferably by light wrench tightening. Flexible extensions should be suitably supported.
It should he ensured that the extension is of the correct length and style to suit the required spplication. The sealing extension should be fitted with a valve cap, unless the extension precludes this.
8,6 Tn-service valve checks
New rubber snap-in valves and the rubber components of metal clamp.in valves should always be fitted when fitting new replacement tyres.
Rubber covered valves should be examined reu1arly for splits and cuts. Damaged valves should be replaced immediately.
All valves should he examined regularly for damaged cap threads and/or distorted valve mouth where the cap is fitted. The internal valve core threads should also b examined for cleanliness. If the valve mouth is distorted the valve should be replaced.
The metal parts of tubeless or tube valves can become damaged or distorted during their service life. Distortions may have weakened the valve to a point of possible fracture and in such cases the valve should be replaced immediately.
It should be ensured that the radiused valve mouth which contacts the cap sealing washer is smooth and without nicks and burrs which may scuff and tear the cap seal.
Damaged cap threads, internal core threads and valve mouths should he repaired with an appropriate and recommended repair tool.
8,7 Check list for care of inflation valves for commercial vehicles
The following check list should be used for care of inflation valves for commercial vehicles.
a) Do ensure the valve and valve fitting is the correct Do not assume that “any.olC valve or valve size and type for the wheeLs and usage. e.g. it is fitting is suitable.
essential that clamp.in valves are used for inflation
pressures above 475 kPa (4.7 bar or 69 psi).
b) Do regularly check on valve cores for leakage. Do not attempt to cure leaking valve core by
Replace damaged or leaking cores. over.tightening. Damage to core seat can
easily result.
c) Do ensure that valve caps are always fitted and Do not leave valve caps on the ground when
replaced after removal, Sealing type valve caps are servicing. They can become damaged or lost
preferred.
Do not attempt to remove pits, rust and burrs by grinding or heavy filing. The holes may become irregular in shape and affect valve sealing.
Do not attempt fitment of a snap-in type tubeless valve without the correct mounting tool. Do not use grease or dirty lubricant.
Do not use excessive force to tighten clamp-in valve securing nuts.
Do not attempt to fill cracks or splits with paint, or attempt to repair valve distortions, nor attempt clearing or cleaning of thread or valve mouth without the appropriate and recommended repair tool.
Do not assume that tyre valves will last forever.
Do not use an extension if inflation and pressure checking can be achieved without it.
Do not overtighten universal screw-on type valves or omit rubber washers nor align valves by unscrewing stem.